The present invention relates to the art of continuous electroplating and is particularly useful for plating terminals provided along one edge of an article, for example a printed circuit board, as is known in the art, as the board is conveyed through various stations for sequential processing.
It is well known in the art to electroplate edge terminals of printed circuit boards where the boards have cooperative terminals connected to "lands" for interconnection of the terminals to associated equipment. The electroplating is accomplished primarily with gold because of the effective corrosion resistance and resistance to erosion of the goldplated contact areas so that reliable electrical contact is maintained between the board components and the associated elements.
The prior art discloses means to cover portions of a printed circuit board with a thin synthetic film during electroplating of the terminals where peripherial portions of the boards are masked with adhesive tape to prevent undesired plating of certain areas of the board or electrically connecting the lands or damaging the lands. In such procedures the board is dipped in a level controlled electroplating solution which is electrically charged with electricity for plating. The procedure in general includes initially plating the terminals, for example with copper or nickel and finishing the plating with gold to provide sufficient electrical conductive properties and erosion resistance.
U.S. Pat. No. 4,029,564-Higuchi teaches a batch feed operation where terminals of printed circuit boards are gold plated, one board at a time. The reference utilizes mechanical masking means comprising a pair of opposed plates having a masking sheet on the sides thereof and pressure cylinder means co-acting with the plates for clamping the board therebetween to protect the portions of the board not requiring plating. The plating material is sprayed onto the board terminals for plating. The device disclosed in the prior art does not provide continuous movement of boards through the machine for complete processing nor does it provide quick equipment interchangability to handle processing of boards of various thickness and sizes.
U.S. Pat. No. 4,155,815-Francis, et al teaches a continuous plating machine utilizing a cooperating pair of endless tractor tread conveyor means to transport printed circuit boards through a plurality of process stations to complete the operation. The printed circuit boards are captured between the opposing shoes, or treads which serve as a masking means to protect the portions of the board which are not to be plated and the selected areas of the boards are electrically plated. The shoes themselves are supplied with an electrical potential opposite in polarity to the potential of the plating bath so that the electroplating circuit is closed.
The devices in accordance with U.S. Pat. No. 4,155,815 have proved entirely satisfactory in most applications however specialized applications have been found for which the improvements provided by the present invention are particularly useful.